Chemical action where a solid disintegrates (dissociates) into a gas without going through a liquid state or phase. For instance, because the climate in Colorado is so dry snow does not always melt into liquid water but will sublimate directly into water vapor disappearing from the ground directly into the atmosphere. Another example is faded paint on a road sign is the paint sublimating (disintegrating) into the air by chemical action of heat, oxygen and ultraviolet light. Likewise water evaporating from the surface of the ocean is actually the complex or compound water molecules disintegrating into simple molecules and/or atoms of water.
(courtesy Wikipedia) (click to enlarge)